By Eliza Normen, Megan Dunlop and Emily McleanAP Biology Period 6

Purpose

To study how time effects rate of osmosis

Hypothesis

If the weight of the potato increases over time and the potato is going through the process of osmosis, than time effects rate of osmosis

Procedure

First make a solution of sugar and water This solution will be 5% sugar Table sugar is a disaccharide of glucose

and fructose Its chemical formula is C12H22O11 Add 5 grams of sugar to a graduated

cylinder. Add distilled water until you reach 100

mL of solution. Poor 25 mL of solution into 4 cups

Procedure (cont.)

Cut 4 potato wedges of relatively equal size Weigh the potato pieces Add each potato piece to 25 mL of the

sugar solution Label the cups of solution 1, 2, 3 and 4 Allow potato 1 to remain in the solution for

10 minutes, potato 2 for 20 minutes, potato 3 for 30 minutes and potato 4 for 40 minutes

Dry off outside of potato piece, weigh and record results

Potato

Experiment

Controls Variables

Amount of time potato was in solution

Molarity of the solution

Potato Type/Potato size

Type of sugar used to make solution

Change in weight due to time spent in solution

Experiment

Test Tube

Observations

Solution was clear and colorless Potatoes were light tan in color After osmosis, potatoes 3 and 4

looked slightly larger than before, as if they had swelled

When potatoes were removed from solution, extra solution remained on the outside

Data

Potato Number

Original Weight of Potato (g)

Weight After Osmosis (g)

Change in Weight (g)

1 5.7 5.8 .1

2 5.4 5.5 .1

3 5.3 5.45 .15

4 5.8 6.0 .2

Change in Mass

Potato Number

Original Weight (g)

Change in Weight (g)

Percent change in Weight

1 5.7 .1 1.75%

2 5.4 .1 1.85%

3 5.3 .15 2.83%

4 5.8 .2 3.45%

Graph

ConclusionDoes Time effect Osmosis?

Time does effect osmosis The longer the potato was in the

glucose solution, the more the water went into the potato

The water went from high to low concentration through the process of osmosis to attempt to reach equilibrium

Restate Purpose

The purpose of this experiment was to see if time effects osmosis

From our experiment, we can conclude that the answer is yes

Hypothesis was Correct!

Our hypothesis predicted that time would effect osmosis

If the weight of the potato increased after a certain amount of time in the solution, than time does effect osmosis

Experimental Errors

Human error: The potatoes may not all have been in exactly the same amount of solution

All remaining solution might not have been dried off from outside of potato

Equipment error: The balance beam may not have accurately recorded the weights of the potato

What would we do differently? Make all the potato pieces the exact same

weight and size Try a different solution, such as salt

dissolved in distilled water Keep potato pieces in solution longer before

measuring change in weight Try a different fruit or vegetable, like an

apple Test to see if there a point at which the

potato reaches equilibrium and time no loner effects osmisis

Osmosis

Osmosis is the diffusion of water across a membrane

Water naturally moves from areas with high concentration of water to low concentration

It moves from areas with a low concentration of solute to a high concentration

This process does not use energy

Osmosis Across a Membrane

What we learned

A semi-permeable membrane allows some substances to move into and out of the cell, while it blocks other substances from moving across the cell

The flow of water is regulated by aquaporins (proteins located in the cell membrane)

Time effects osmosis. The longer the potato was in the solution, the more water diffused into it

Aquaporin

Side View

Sources for Pictures

http://www.aquapuredrinkingwater.com/reversepic.jpg

http://images.asia.ru/img/alibaba/photo/50353563/Potato.jpg

http://www.made-in-china.com/image/2f0j00EMptukCsgHqvM/Test-Tube-10ml-7ml-5-5ml-G1001-G1002-G1003-.jpg

http://img.tfd.com/wiki/a/a5/Aquaporin-Sideview.png